Electrical potentiometer



y 5, 1948. A. R. E. ARNOT 2,442,228

ELECTRICAL POTENTIOMETER Filed April 25, 1946 P 9 Fig.2

2 Z2JJ6ZUZOZ Patented May 25, 1948 ELECTRICAL POTENTIOMETER Alfred Reginald Erwin Arnot, London, England, assignor to Rotax Limited, London, England Application April 25, 1946, Serial No. 664,776 In Great Britain March 5, 1945 Section 1, Public Law 690, August 8, 1946 Patent expires March 5, 1965 1 Claim. 1

This invention has for its object to provide an improved electrical potentiometer, adapted for use more particularly with electrical remotecontrol apparatus.

The invention comprises the combination of main resistance adapted to be connected to a current-supply circuit, a relatively short subsidiary resistance connected in series or parallel with the main resistance, a movable member, a single contact carried by the said member in association with the main resistance, and two sets of alternately disposed and equi-spaced contacts adapted to co-operate with the subsidiary resistance, the arrangement being such that during the movement of the single contact along the main resistance, not less than one and not more than two of the other contacts shall at any time be in contact with the subsidiary resistance.

In the accompanying sheet of explanatory drawings:

Figure 1 is a plan, and Figure 2 a part sectional side view, of a potentiometer embodying the invention.

In carrying the invention into eiiect as shown, I employ a main resistance a made from wire wound on a former b of annular form, the two adjacent ends of the wire being adapted for connection to a current supply circuit. Concentrically With the main resistance a is arranged a subsidiary resistance made from wire wound on a former d of segmental form, the ends of the subsidiary resistance being connected to the ends of the main resistance. The two resistances a, c and their formers b, d are carried by an insulating support 1.

Rotatably supported by a ball or other bearing g in a central hole in the support is a member h carryin a plurality of contacts. One of these contacts is indicated by i, and is formed by an arm arranged to move around the main resistance a. The other contacts are divided into two groups each consisting of, for example, four equi-spaced contacts, those in the one group being indicated by 1, and those in the other group being indicated by Is. Also the contacts 7' are formed by arms on an annular member m, and the contacts k are formed by arms on another annular member n, the two annular members and the first mentioned contact arm 2' being mounted on the contact-carrying member h with insulating spacers 0 between them. Moreover, the contact arms a alternate with and are situated midway between the contact arms lc, and all of these contact arms are adapted to co-operate with the subsidiary resistance 0. The are subtended by the subsidiary resistance e is such that not more than one contact arm 9' and one contact arm k can be in contact with this resistance at any time.

The two groups of contact arms 7', k are respectively connected to two slip rings 11, q on the support 1, and the single contact arm 2' is con nected either to a third slipring r on the support or to the spindle of the rotary contact-carrying member h, the connections between the contact arms and the circuits to be controlled being effected through brushes or other means co-opcrating with the sliprings, or with the sliprings and spindle. Actuation of the rotary member h may be effected by hand, or by electrical or other means.

During rotation of the rotary member h between its limits of movement, which are separated by approximately 360, the single contact arm 1 progressively varies the ratio of the two parts of the main resistance a on the opposite sides of this contact arm. Meanwhile, the contact arms 1', k, of the other two groups successively pass over the subsidiary resistance 0, there being never less than one such contact, or one of each group of such contacts, on the subsidiary resistance at any time.

A potentiometer as above described is intended for use more particularly in the electrical distant control system described in the specification of my co-pending application No. 664,777. This system employs two of such potentiometers, the rotary member of one of which is operable by hand, and that of the other by an electric motor which is responsive to the movement of the hand operated member. The main resistance controls an electromagnetic relay which in turn through electromagnetically actuated contactors controls the electric motor for actuating a mechanism which is required to move only in response to the wishes of a distant operator. The subsidiary resistance controls a pair of circuits associated with a second relay also operating on the said contactors.

The arrangement is such that any movement given to the hand operated member of the one potentiometer is reproduced by movement of the corresponding member of the distant potentiometer, the motor being brought to rest automatically when the second potentiometer is brought into a state of balance with the first.

The invention may, however, be applied to other analogous uses, and subordinate details may be modified to suit different requirements. Thus, for example, instead of arranging the two resistances in parallel as above described they may be arranged in series.

Having thus described my invention, What I claim as new and desire to secure by Letters Patent is:

A potentiometer comprising the combination of a main resistance adapted to be connected to a current-supply circuit, a relatively short subsidiary resistance connected in series or parallel with the main-resistance, a movable member, a 10 

